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Thursday, May 22, 2008

I'm on the downswing of many days in the field - so it's Thursday for me (after Wednesday hump day whenever that was) and Thursday for real.

It seems like it's been a rough day at work, although most of the day really was fairly routine and not so unusual. I think the roughness has had to do with the fact that 1) it's probably my 17th day here at work and 2) I seemed to be rather sound sensitive most of the day, which is usually related to an oncoming migraine. And then, 3) at the end of the day, some disagreements arose, more or less from another part of our little world - and it all seemed either 1) a little overdone or 2) a little over-dramatic. But then, I was probably 3) a little over-sensitive.

One thing became clear from this discussion: as a geologist, one interpretation I make routinely is the rock type! You'd think that rock type would be a factual piece of information, but it's actually an interpretation, especially before geochemistry or whole rock chemistry has been done, and especially before any petrography (microscopic thin-section work) has been done. For example, if I say a rock is a limestone or a shale, that's actually my best interpretation of what I'm looking at. If I, on the other hand, say this rock is a very fine-grained, light gray rock that fizzes "like crazy" (or maybe I add that it's made of 100% calcite) - that's a description. The rock might not be a limestone. It could be a strongly carbonate-altered sandstone! Or something else entirely!

Another interpretation, one that is highly suspect in the particular area I work in (and in or near many mines and old mining districts), is the rock formation. Is this the Navajo Sandstone or the Redwall Limestone? Now, you would think that I should be able to tell those two formations apart (for example), but in this area they are both at least a little hydrothermally altered, if not strongly altered. The only outcrops of these formations are unaltered versions of the supposedly same highly altered formations as intercepted at depth in drill holes. So, both rock type and rock formation are interpretations! I suppose this really doesn't or shouldn't come as a surprise, but today the concept really sank in.

As for the migraine, I think I feel better having typed all this stuff out [and also for now - later - having edited most of it away!].